This invention relates to an acoustic emission automotive crash sensor arrangement for sensing the acoustic emissions of a crash caused deformation of vehicle structure and generating a crash signal to activate an occupant restraint if the acoustic emissions meet particular criteria.
The use of acoustic emissions for crash sensing was disclosed in U.S. Pat. No. 4,346,914, issued to Gerald D. Livers et al on Aug. 31, 1982. In the system disclosed in that patent, a continuous loop type wave guide is welded to the vehicle front structure at a plurality of points so as to conduct acoustic emissions from the structure to one or more acoustic sensors located on the vehicle firewall. The sensor output is compared with a preprogrammed threshold for one or more parameters of the acoustic emission event to determine whether the event is the product of an impact of severity sufficient to require activation of an occupant restraint.
The waveguides of the Livers et al system, however, can add additional cost and weight to the vehicle and complexity to the vehicle engine compartment. It would be desirable to sense the acoustic emissions from vehicle structural deformation without such waveguides in such a way as to reliably determine the necessity for activation of an occupant restraint. In addition, it would be desirable to determine the precise criteria for which such a signal should activate an occupant restraint and for which it should not so activate it.
The majority of today's vehicles are built with unit body construction, wherein the major parts of the vehicle structure are welded together. Thus, the waveguides are not necessarily needed in such vehicles to allow communication of acoustic emissions from a deformation near the front of the vehicle to a sensor located on the vehicle structure, if the locations of the sensor or sensors are chosen correctly and if a crash sensing algorithm can be discovered which accurately distinguishes between those acoustic emission events for which occupant restraint activation is desired and those for which it is not in response to a signal from the sensor(s).